According to a blog post at the Wall Street Journal here, the U.S. Postal Service, between 1999 and 2005, purchased about 30,000 flex-fuel Ford Explorers in order to satisfy a 1992 mandate that a certain percentage of government vehicles be capable of running on alternative fuels.

The problem was that there was only limited availability of E85, so most of the vehicles were run on regular gasoline, but got 29% fewer miles per gallon than the vehicles they replaced.

Woops, nothing "Green" about that. Wouldn't it be cool to see Walt the Postman driving a Honda Fit, or maybe a Ford Escape hybrid? Either would've been a way better choice.